Heat exchanger



Aug. 11, 1953 o. A. CARNAHAN 2,648,527

HEAT EXCHANGER Filed May 25, 1948 4 SheetsSheet l Aug. 11, 1953 o. A. CARNAHAN HEAT EXCHANGER 4 Sheets-Sheet 2 .iiii

Filed May 25, 1948 V A u Aug. 11, 1953 o. A. CARNAHAN 2,648,527

HEAT EXCHANGER Filed May 25, 1948 4 Sheets-Sheet 3 l f a j Z /0 O O O B 00 0 00 a 000 l a 1 WWQ Qi Q O 0 0 3 1, T

Aug. 11, 1953 o. A. CARNAHAN HEAT EXCHANGER 4 Sheets-Sheet 4 Filed May 25, 1948 v fa /a jlllllllllll aria? Patented Aug. 11, 1953 UNITED STATES PATENT OFFICE 6 Claims.

This invention relates to external combustion gas engines and more particularly to improvements thereof which enable such engines to operate with an efficiency approaching the theoretical value and to perform with characteristics desirable for driving both stationary and mobile devices.

It is an object of this invention to provide an improved external combustion gas engine wherein a thermo-gas compressing unit serves as a gas compressor for supplying gas under pressure to a storage receiver for use in operating both auxiliary equipment and also one or more gas engines which may be remotely positioned from the receiver and compressor.

In brief, external combustion gas engines which have heretofore been known in the art have been subject to many limitations. Such engines employ a loosely fitting air moving plunger which serves to move air from a cool to a hot portion of a cylinder and vice versa. The periodic heating and cooling of the air causes a change in pressure which serves through a power piston to operate the output shaft of the engine. A source of heat such as burning fuel is employed to heat the gas in one end or portion of the cylinder, and a heat extracting device is employed at the opposite end of the cylinder in order to reduce the temperature of the gas after it had passed from the hot end of the cylinder to the cold end of the cylinder. During the transfer of gas between the cylinder ends, it passes through a heat regenerator or storage means which serves to absorb a portion of the heat from the heated gas and to liberate the stored heat to the gas as it passes from the cooled end of the cylinder to the hot end. The resulting expansion and contraction of the gaseous medium was employed to move a piston to provide the power output from the engine.

The best known engines employing this principle of operation are those disclosed by Sterling, Rider, E'riccson and other early pioneers. These engines found limited use and were subject to the disadvantage resulting from the necessity of being constructed in large size with a resulting heavy weight. The time necessary for the transfer of heat in the above described cycles of known engines is so great that the engine must be operated at slow speeds, that is, with relative few cycles per minute. It is apparent that the smaller the number of cycles in a given period of time, the greater must be the energy made available per cycle and hence the greater the size of the engine which is necessary in order to deliver a given amount of power.

While the mechanical features of the previously known external combustion gas engines have differed, they have all followed the general pattern of employing the expanding and contracting gas within the heated cylinder to move a piston from which power was derived through mechanical linkages. Due to their mechanical limitations, it has been impossible satisfactorily to power mobile devices such as automobiles, ships and the like with these engines. Further, the efficiency has been low in respect to the efiiciency which may be theoretically attained. Also, it has been impossible due to mechanical and material limitations to provide an external combustion gas engine having an efiiciency and a power output comparable with engines designed to operate on other principles such, for example, as the internal combustion engine.

It is, therefore, another object of the invention to provide an improved external combustion gas engine which may be operated at high efiiciency throughout a varying pressure range and over a wide range of speeds and torques.

Another object of this invention is to provide an improved external combustion engine, the output of which is independent of atmospheric pressures and is increased with lowered atmospheric temperatures.

Another object of this invention is to provide an improved engine of the external combustion type which may be operated at high efficiency on any liquid, or gaseous fuel, including oils having volatility and low B. t. u. content.

Another object of the invention is to provide an improved external combustion engine which may be readily reversed in direction, is nonstallable upon the sudden increase of load and which may be immediately started under load upon the opening of a control valve.

A still further object of the invention is to provide an improved external combustion as engine having associated as parts thereof automatically actuated accessory devices which enable the engine to operate as a self-contained unitary motor having flexible performance characteristics.

A still further object of the invention is to provide an improved engine of the external combustion gas type which is lubricated by oil contained within the compressed gas system and which circulates over the moving surfaces of the gas engine during its operation without coming into contact with ambient air or without being elevated to high temperatures.

It is a further object of this invention to provide an improved external combustion gas engine comprising a thermo-gas compressing unit for supplying gas under pressure to operate a gas engine wherein an inert gas is employed as the Working medium in order to prevent corrosion of the parts with which the gaseous medium makes contact and to eliminate deterioration of lubricants during operation of the engine.

A still further object of the invention is to provide an external combustion gas unit which supplies, in addition to output power, both a cold medium which may be used for refrigeration and cooling of confined spaces, and a hot medium which may be utilized for heating confined spaces.

A still further object of the invention is to provide an improved thermo-gas compressing unit provided with heat transfer means which enable the gaseous medium within the unit to be heated and cooled with a minimum loss of heat and in a minimum amount of time.

A still further object of the invention is to provide an improved gas moving plunger for use in a gas compressing unit. which is designed to reduce the fiowage of heat through the plunger from the hot head or end of the thermo-gas compressing cylinder to the cold head or end.

A still further object of the invention is to provide an improved heat exchanging unit which will efiiciently transfer a large amount of heat from theexternal heat source to the gas within the thermo-gas compressing unit.

A still further object of the invention is to provide improved heat exchange units which may be inexpensively fabricated, are efiicient in operation, and are easily inserted in both the compressed gas and coolant lines of the external combustion gas engine.

A still further object of the invention is to provide an improved external combustion gas engine. in which combustion takes place in a chamber the intake and discharge passages of which'are constructed to suppress noise, to ofier negligible resistance to the ilow of gases, and to prevent the possibility of igniting gas or other material outside the combustion chamber.

A still further object of the invention is to provide an improved engine of the external combustion gas type which may be effectively employed as a power source for automotive vehicles in lieu of, and as a substitute for, the conventional internal combustion gas engine, speed changing transmission, clutch and difierential ea n still further object of the invention is to provide an external combustion gas engine which may be constructed of relatively few parts that may be easily and quickly assembled and disassembled for inspection and replacement of worn parts.

The invention also resides in certain novel structural characteristics which facilitate the carrying out of the foregoing objects and Which contribute both to the versatility of performance and to its ruggedness of construction as well as to its dependability and efiiciency of operation. n

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, in which:

Fig. 1 is a diagrammatic drawing of the improved external combustion gas engine showing the accessory devices therefore and the gas engine from which the power output is derived.

Fig. 2 is a side elevation of the heat exchange unit employed to preheat the combustion air by the products of combustion flowing through the flue.

Fig. 3 is a cross-section taken on line 33 of Fig.2.

Fig. 4 is a cross-section taken on line 44 of Fig. 2.

Fig. 5 is a cross-section taken on line 5--5 of Fig. 2.

Fig. 6 is a perspective view of the spacer element positioned between the plates of the heat exchange unit shown in Figs. 2 to 5, inclusive, and Figs? and 8. I I

Fig. '7 is a side elevation of the heat exchange unit or radiator employed in the coolant system of the thermo-gas compressing unit.

Fig. 8 is a cross-section taken on line 8-8 of Fig. 7

Fig. 9 is a side elevation of the element closing the hot end of the cylinder in the thermogas compressing unit.

Fig. 10 is a View partly in cross-section and partly in plan, taken on' line lfll0 of Fig. 9 showing passages for the gas within the thermogas compressing cylinder.

Fig. 11 is a view partly in cross-section and partly in plan taken on line I|-ll of Fig. 9 showing passages for the products of combustion.

Fig. 12 is a cross sectional view showing the details of the gas moving plunger, its supporting means, and the closure of the cool end of the thermo-gas compressing cylinder, including coolant and gas passages.

Fig. 13 is a view partly in section and partly in plan taken on line l3l3 of Fig. 12.

Fig. 14 is a view which discloses a modification of the gas moving plunger, its supporting means, and the closure of the cool end of the thermo-gas compressing cylinder including coolant and gas passages.

Fig. 15 is a cross sectional view taken on line iE--i 5 of Fig. 14.

While this invention is susceptible of various modifications and constructions, I have shown the drawings and will herein describe in detail the preferred en'ibodiment. It is to be understood that I do not intend to limit the invention by such disclosure and I aim to cover all modifications and alternative construction falling within the scope and spirit of the invention as defined in the appended claims.

In reference to Fig. l, the thermo-gas compressing unit is indicated by reference numeral l. The gas drawn into the thermo-gas compressing unit is obtained from gas containing receiver 58 and after compression within the unit it flows to gas containing receiver 60. The gas cmployed in this flow cycle may consist of air or may be selected from inert gases such as nitrogen, helium, carbon dioxide or the like. The output of the external combustion gas engine is derived from the shaft of the gas engine ll!!! which is directly connected through piping and control valves to the gas containing receiver and its exhaust outlet is connected by piping to gas containing receiver 56. Gas engine I86 may be areciprocating non-expansion, or expansion engine, or it may be of the turbine type. For the purposeof this disclosure, engine me will be described as a reversible, 'z'nulti-cylinder, single expan'sion, compressed gas motor. An auxiliary compressed gas motor 28 is also connected to the gas containing receiver 89 and the power output of this motor is employed to operate the gas moving plunger 2, a combustion air blower 3'5 and an auxiliary gas compressor 96, as Well as the valve 3! of the auxiliary compressed gas motor 20. Additional control devices are employed in the engine, including a thermostatic fuel control Tl, a pressure ratio fuel control device 55, anunloader valve 85, auxiliary gas compressorSfl, pre sure control mechanism I23, together with'the fl -l pressed gas control valves.

In more detail the improved engine sho n i Fig. 1 employs a thermo-gas compressing unit having a cylinder 45, provided with a cold body or head l at one end thereof and a hot body or head 3 at the opposite end thereof. In heat exchange relation with the hot head of cylinder i5 is a combustion chamber ii provided with an onclosing wall 5 t and a conventional high temperature lining ll. Within the combustion chamber MI is a fuel burner E 3. Air to support combustion is supplied to combustion chamber ii! by blower 35, outlet thereof 55, and inlet 38 of the combustion chamber. The products of combustion or flue gases pass from the combustion chamber M3 through heat exchange passages 3, outlet 42 to the flue or stack 63. As is shown in Fig. 1, both the incoming combustion air and outgoing products of combustion are passed through a heat exchange unit 57, the construction of which will be later described in detail.

The interior of the cylinder l5 of the thermogas compressing unit i is divided into two charnbers indicated by reference numerals H] and H by a movable loosely fitting gas moving plunger 2. This plunger is dimensioned to move in the cylinder in very close proximity to the wall thereof without making actual contact. Chamber if! is positioned adjacent to the hot cylinder head 3 of cylinder i5 and chamber 5 i is positioned adjacent to the cold cylinder head i. The gas moving plunger or piston 2, which does not serve to compress the gas within cylinder it but serves only to move the gas from chamber iii to chamber H and vice versa, is operated by a piston rod 25 which extends through a bore and packing gland E9 of the cold cylinder head I.

The hot head 3 of cylinder 65 and the associated heat exchange unit are shown in detail in Figs. 9, l and 11, and comprise on the combustion chamber side thereof a plurality of radially extended passages S H. The heat resistant lining ii of the combustion chamber id abuts against the lower side of the hot cylinder head 3 to form a barrier which serves to direct the combustion gases through radial passages E li so that the heat of the gases will be absorbed by the material of the hot head 3. The portion of the hot cylinder head 3 positioned within chamber i is likewise formed with radially extending passages which serve as heat exchange means for transferring heat to the gas within chamber it.

As is shown in Figs. 1 and 10, passages 36 extend from an opening positioned in the chamber iii centrally of the hot cylinder head 3. The hot cylinder head 3 is formed of heat conductive material which will retain its rigidity and force at extremely operating temperatures.

The radially extending gas passages 334 communicate with a plurality of passages 5 formed of heat absorbing material positioned around the interior wall of cylinder 15. These passages and the material in which they are positioned form the regenerator of the improved engine and serve alternately to absorb and liberate heat during the periodic transfer of gas between chambers l 0 and ii. Passages 5 communicate on the cold end of the cylinder with passages 486 preferably formed integral with cold cylinder head 1. The passages its extend in a radial direction from the opening dill positioned in the central portion of the cylinder head i. Thus, passages 05 in the cold cylinder head, passages 5 adjacent to the wall of cylinder 25, and passages 364 formed integral with hot cylinder head constitute communicating paths between cylinder chambers in and II through which the gas within the cylinder is transferred by reciprocating movement of the gas moving plunger 2.

The cold cylinder head 1 is provided with a hollow interior as is indicated by reference numeral 9 through which a coolant is passed. The coolant may comprise any suitable fluid which will serve to transmit heat from the portion of head 7 through which heat passes from the interior of chamber H. The coolant containing space is connected by pipes 8 to a heat exchange unit 3M which is best shown in Figs. 7 and 8. Flow of coolant in the closed system through pipes 3 between the heat exchange unit 314 and chamber 9 results in the transfer of heat from chamber H to the heat exchanger from which it is liberated to the space in which the heat exchange device is located. The details of the heat exchange unit 3M shown in Fig. 1 will be described later.

As the gas moving plunger 2 is moved from a position adjacent to a cold cylinder head 1 to a position adjacent to a hot cylinder head 3, hot gas from chamber It is forced through passages 304, the passages of heat regenerator 5, and passages 406, and to chamber H. A large portion of the heat contained in the gas being thus transferred or moved is absorbed by the regenerator material during its flow through passages 5 and additional heat in the gas is absorbed during flow through passages and dissipated by the coolant flowing in the chamber 9 of the cold cylinder head 'I. As the gas cools the pressure falls below the pressure of the gas in receiver 56 and thus check valve [3 opens to permit gas to be withdrawn from receiver through pipe 5!, check valve [3, and pipe I2 into chamber ll.

As the gas moving plunger 2 is moved from a position within chamber I 0 adjacent to hot cylinder head 3 to a position within chamber ll adjacent to cold cylinder head 7, the cooled gas flows in an opposite direction; i. e., through passages 405, the passages within the heat regenerator 5 and passages 304 to chamber l0. During this period of flow through passages 5, the heat stored in the regenerator is liberated and the gas temperature is raised. It is further increased during flow through passages 304 since these are in direct heat transfer relation with the combustion chamber 40. As a result of the increase in gas temperature, the pressure rises to that in receiver so that gas is discharged from chamber ll through pipe I2, check valve [4 and pipe 6| to gas containing receiver 60. Thus, a pressure differential is established in receivers 50 and 69 which is utilized in operating the gas engine lllfi as will be hereinafter described.

As has previously been described, the gas moving plunger 2 is reciprocated in cylinder [5 by an auxiliary compressed gas motor 20 which is actuated by the compressed gas from receiver 50. This gas passes to the auxiliary compressed gas motor 20 through check valve HI], pressure control mechanism I23, pipe I I l, and valve chest 39 of motor 20. Piston valve 3! controls the direction of flow of compressed gas so that it will act upon opposite faces of piston 2! of motor 20. The reciprocating motion of piston 2| operates piston rod 22 which is connected to rocking beam 23. This beam is fulcrumed at 66 and has its opposite arm connected to piston rod 24 of gas moving plunger 2 by any suitable connecting means. A bell crank 29 also fulcrumed at 66 has one arm connected through a pivotal connection 61 to a linkage 30 which is connected assessor to the operating rod of piston valve 31. The opposite arm of bell crank 29 is pivotally connected at '68 to rod 28 which in turnis connected to crank arm 25. -A flywheel 32 is'mounted for rotationonishaft 21 and power 'isapplied thereto by crank arm '25 which is pivotally connected to the rocking beam '23 and :crank '26 which is attached to flywheel 32. Thus, motion of the reciprocating :piston .21 in auxiliary compressed gas motor is transmitted through piston rod 22 to rocking beam 23 whereby :gas moving plunger 2 is reciprocated within cylinder 15, the flywheel 3 2 'is driven by crank armi and .piston valve 3i is actuated through bell crank 20, pivotal connection 61 and linkage 530. The rotary motion of the flywheel 32 derived in this-manner serves to operate theian-of combustion :blower through belt '33 and apulley :34.

The reciprocating movement of piston -2I is also transferred through piston rod 22 to piston 9| whichis mounted ffOl reciprocating movement in the cylinder 04 of auxiliary gas compressor 90. Reciprocating movement of piston ill serves to draw gas through pipe 86, valves 92, to the cylinder 90 from whichit is discharged, through valves '93 into gas containing receiver 80 through pipeBI.

The operation of auxiliary gas compressor :90 in the manner describedserves to pump gas from pipe 06. pipe 66 will be evacuated, after which the gas compressor 90 will become inoperative. If valve I is open, and the pressure in gas containing receiver is greater than atmospheric, gas will be pumped from receiver 50 by gas compressor 90 010 receiver T80. The fiow of .gas during this pumping operation may be traced from receiver 50 through pipe H3, .heat exchange unit I35, the central opening .of piston valve -I 0I, valve chest I05, the central opening :of second piston valve I01, pipe I Ii2,'va1ve chest 39, the central opening-in :piston valve .31, pipe I-4I, valve 1'40, to pipe .86 and the auxiliary -gas compressor 3530. Upon the reduction of pressure within receiver 50 to a predetermined value below that of atmospheric pressure, compressor 90 will become inoperative. "This reduction is pressure -reoeiver '50 is reflected in receiver 00 and also in the rthermo-igas :compressing :unit 'I, and results in :the slowing t idling speed of compressed gas motor .20, compressing unit I, and combustion blower -35.

-If, however, the pressure in receiver 00 is less than :the predetermined pressure setting of pressure controlledun'loader valve-05, the check valve 84 will open to allow atmospheric air "to enter pipe 06 which will be compressed by compressor 90 .and discharged .to receiver 60. It will be noted that the compressor unloader valve 285 is connected to pipe BI and the pressure of receiver 80 is communicated to pressure diaphragm =82. When vthis'pressureiis increased to a value greater than the preselected valueas determined by the weight setting, .the check valve actuator'83 'is operated .toumaintain valve 84 in closed position. When, however, 'ithe selected pressure value is less than the pressure in receiver 00, the valve actuating rod:33 is moved by diaphragm'62 to permit check valve i81lto open, and'thus permit atmosphericair to enter line 06. In this-manner, make-Lupair isadmitted to replenish the loss of :gas due to -possible leakage innthe system. If the working :gflS: medium of the. engine comprises an inert gases previously discussed, the inert gas from. anyesuitable container is fed to un- When valve I'40 is closed the gas "in loader valve and permitted to flow through valve .84 in lieu of the atmospheric .air.

As previously set forth, gas engine I00 may be either an expansion or non-expansion type ongine or it may be of the turbine type employing a rotor. For the purpose of understanding this invention, engine I00 will be described as a reversible, multi-cylinder, single expansion compressed gas motor such as is conventionally .employed to derive power from compressed air or steam. The engine as shown in Fig. l is provided with two cylinders H4 and H5 each of which is equipped with a piston I02 which is adapted 'to reciprocate within its respective cylinder. The pistons are connected by piston rods I03 to connecting rods I04 by cross head pins H6. The reciprocating movement of pistons I02 is employed to drive output shaft I06 which is driven through cranks Ii! and H0. These cranks are angularly offset by approximately degrees in order to provide uniform torque during each revolution and to eliminate the disadvantage which would otherwise occur if the pistons came to rest on dead center. Piston valves I0-I are provided in valve chest I05 and are reciprocated by valve stems I08 which are connected to eccentric rods I071 by reversing links H9. The eccentric rods I0'l are driven by eccentrics I25 which in turn are driven from the crank shaft Gas engine W0 is connected to receivers 60 and 80 by pipes E32 and i2I, and connections I20 and I21. The main throttle valve I20 for the engine is connected to pipes I32 and I2I, and located intermediate the engine and connection I26. The gas engine I00 exhausts through pipe I23 which is connected to receiver50. Heat exchange unit I35 is connected in pipe II 3 as shown in Fig. 1. This unit is similar in construction to heat exchange unit 31 and its function will be described. in detail later.

Pressure control mechanism I23 is connected to pipe I2I by piping E22 and on the opposite side thereof to connection I26, whereby, as will be seen in Fig. 1, it is placed in parallel relation with main throttle valve I20. Thus the pressure across valve I20 will react on piston I28 of the pressure controlled mechanism I23 and when the pressure different on the opposite sides of valve I20 .is reduced the pressure exerted by spring I24 will move piston I 26 and piston rod I20 to operate valves I30 and I40. t will be noted that movement of piston rod I29 acts through a toggle connection I3I to rotate the actuating arms of valves I30 and I40. The operation of the pressure controlled mechanism I23 as well as the purpose of valves I30 and I40 will become apparent during the description of the engine operation.

The fuel supplied through pipes 15 and I6 from a source (not shown) to fuel burner I8 in com- .bustion chamber 00 is controlled by a thermostatic fuel control device IT and a pressure ratio fuel control device 55. The thermostatic fuel control device 'I'I comprises an extensible bellows 'II, the interior of which is connected to a bulb I0 positioned in the outlet 02 of the combustion chamber. The interior of bulb I0 and bellows .lI is filled with an expansible fluid which causes the bellows to expand when the bulb I0 is affected by increased temperatures. A valve 12 is actuated by bellows H to close the fuel supply pipe I6 upon the occurrence of a predetermined temperature within the outlet of the combustion chamber. Upon the occurrence of temperatures less than a predetermined value the bellows contract to open valve I2 and permit fuel to flow from the source to burner [8.

The differential pressure ratio fuel control valve 65 which also serves to control the flow of 5 fuel to burner I8 is directly connected with opposing diaphragms 52 and 62. One side of diaphragm 52 is connected directly to, and affected by the pressure in gas containing receiver 58 and the opposing side of diaphragm 62 is con- 10 nected to and affected by the pressure existing in gas containing receiver 60. These diaphragms are connected by the valve rod 56 which actuates the pressure ratio fuel control valve 65. As is shown in Fig. 1, diaphragm 52 has a greater area 5 than that of diaphragm 62. By this opposed arrangement of diaphragms, pressure ratio fuel control valve 65 is caused to close when the pressure in receiver 60 multiplied by the area of diaphragm 62 is greater than the pressure of receiver 50 multiplied by the area of diaphragm 52. Conversely, control valve 65 will be opened to permit fuel to flow to burner 18 through pipes 15 and 16 when the pressure in receiver 56 multiplied by the area of diaphragm 52 is greater than the pressure of receiver 60 multiplied by the area of diaphragm 62. By this arrangement a ratio of pressure existing in receivers 50 and 60 may be selected above which control valve 65 will be closed and below which this valve will be opened to permit the flow of fuel to burner I8.

The details of construction of the heat exchange unit 31 are shown in Figs. 2 to 6 inclusive, wherein reference numeral 236 (Fig. 2) indicates the inlet for the combustion air from the blower 5 35, and reference numeral 238 represents the outlet to the combustion chamber inlet 3%. Numeral 242 indicates the inlet to the heat exchange unit for the products of combustion received from outlet '42 of the combustion chamber, 40 and numeral 263 represents the outlet from the heat exchange unit 31 to the flue or stack 43.

It will be apparent that the passages will be closed by suitable plates (not shown) positioned on the opposite sides of the heat exchange unit @345 from the inlets and outlets above described in order that the gases will be directed and flow through the passages provided in the unit. Air

to the combustion chamber and the products of combustion from the combustion chamber flow in opposite directions through the heat exchanger in order to increase the exchange of heat between the gases in the unit. The heat exchange unit 3'! is built up of a plurality of formed sheets 231 which are secured between face plates 202;, by rivets or bolts 209. The sheets 23'? which form the heat exchange surface of the unit are preformed as indicated in Figs. 3 to 5 inclusive and each adjacent sheet is reversed in position in order to form spaces therebetween for the; combustion air entering the combustion chamber and for the products of combustion leaving the combustion chamber. The plurality of sheets 23'! are secured in superimposed relation between plates 20?. by rivets or bolts 209. The spaces between the sheet groupings through which the gases enter and leave the heat exchanger are formed by the use of spacer rings 2% best shown in Fig. 5. The spacer rings are providedwith apertures 2H5 and one of the rings is positioned 7 between each group of two sheets except for the plates at the top and bottom of the heat exchange unit.

As will be observed in Figs. 2 to 6, inclusive, the

Y preformed heat conducting sheets 23] .are ar- 7 ranged in pairs and a plurality of the pairs are secured in superimposed relation between the face plates. Each of the conducting sheets is formed from a fiat sheet and is provided with depressed and raised sections located adjacent to diagonal corners, and each section contains an opening therein. The sheets 23! are assembled with the depressed portions of pairs thereof in alignment and in engagement with each other to provide spacing means between sheets adjacent to each pair of sheets. Apertured spacing rings are positioned in the recesses or chamber formed by the aligned raised portions, and spacing washers are located intermediate the raised and depressed sections and positioned between the fiat surfaces of adjacent sheets. Additional spacing elements 263 and 204 are positioned between the sheets 23? to seal the perimeter of the heat exchange unit when the individual sheets are secured in assembled position.

By this construction the gases entering through the openings 236 and 262, flow in opposite directions through adjacent passages formed by the sheet groupings and leave the heat exchange unit by openings 238 and Thus the air for supporting combustion within the combustion chamber is preheated by passing over the surfaces of the heat exchanger which are heated by the products of combustion leaving the combustion chamber at 52. In view of the fact that the air enters and the products of combustion leave through the narrow passages between the closely spaced sheets 23'? of the heat exchange unit, noise due to combustion will be suppressed and the gases will be cooled to prevent the possibility of igniting any gas or other material outside the combustion chamber.

The heat exchange unit indicated by reference numeral 53am Fig. 1 is similar in construction to heat exchange unit 3?, just described.

The details of heat exchange unit 3 I 4 are shown in Figs. 6 to 8 inclusive, wherein numerals 308 indicate the entrance and exit for coolant from 0001 cylinder head i, Fig. 1. This heat exchange unit is built up of a plurality of formed sheets 33?, spacing washers 15M, and spacing rings 2%, which are secured between face plates 302 by bolts or rivets 3%. The sheets 33'! which are preformed with raised and depressed sections having holes therethrough, as shown in Fig. 8, are assembled in superimposed relationship and secured together between face plates 302 in a manner similar to the heat exchanger 37. Spacing rings 2&6 having apertures 2E6 are placed adjacent the ends of this heat exchanger between pairs of sheets 33?. The sides and terminal extremities of pairs of adjacent sheets are welded together as is indicated by reference numeral 338 in order to obtain a fluid-tight structure for the coolant. Air for cooling may flow either by convection or forced draft between these pairs of sheets. The air passing through heat exchange unit 3M will be increased in temperature by the heat removed from the cold cylinder head 1 of the thermo-gas compressing unit I. This heat will be available for increasing the temperature of a confined space, such for example, as the interior of a vehicle during the operation of the external combustion gas engine.

Since in any expansible gas engine power is produced at the expense of sensible heat energy, the temperature of the gas is reduced during its passage through these engines. This pressuretemperature relation for gases remote from their liquefaction temperatures is given approximately by the formula P2 T2 where P1 and P2 are absolute pressures, and T1 and T2 are absolute temperatures.

For the pressure ratios used in these engines, this gives a very substantial temperature drop so that the gas leaving engine i and flowing through heat exchanger :35 will be much lower than the ambient temperature. Any fiuid medium which is circulated from connection I33 to 134 through heat exchanger i35 may be employed to refrigerate confined spaces such, for example, as the interior of a vehicle body.

Details of the preferred embodiments of the loosely fitting gas moving plunger 2 are shown in Figs. 12 and 14. As shown in Fig. 12, the gas moving plunger is represented by reference numeral 002 and comprises a hollow cylinder closed at both ends to form chamber can. In order to decrease the heat transfer through the gas moving plunger 402, the interior surfaces thereof are finished to present a highly reflective surface and the interior Act is evacuated to a high degree. Gas moving plunger 1-02 is connected to piston rod 524 which passes through cold cylinder head I in which gas passages 4536 and coolant passages or chambers 209 are provided. In order that the interior of the thermo-gas compressing unit may be tightly sealed, packing 125 and gland 426 are employed through which piston rod .24 passes. Gas passages 300 radiate from a central opening illi as is shown in Fig. 13 and the entire cylinder head in which the radial passages are integrally formed is bolted to thermo-gas compressing cylinder by bolts which pass through holes 50! in the circumference of the cylinder head.

Fig. 14 discloses a preferred embodiment of the gas moving plunger 2 and cold cylinder head 7 wherein the gas transferred by plunger 402 is subjected to additional cooling surface. In this embodiment the gas moving plunger 002 is formed in a generally cup shape with the interior thereof provided with a reflective surface and the interior thereof evacuated to the extent previously explained. The coolant passages 409 are elongated along the axis of piston rod 424 and gas passages 40B are positioned circumferentially about the coolant passage 499. When the gas moving plunger 102 is moved toward the cold cylinder head I, the coolant chamber 409 and the gas passages 406 are positioned in the recess portion of the gas moving plunger 402. In this embodiment the coolant surface adjacent the gas passages has been greatly increased in order that heat in the gas entering portion H of the thermo-gas compressing cylinder will be more effectively removed. The relation of the coolant chamber 4-90 and gas passages 405 is shown in Fig. 15 wherein the apertures 40! for securing the cold cylinder head in place on cylinder l5 are shown. In a similar manner, the gas moving plunger shown in Fig. 14; is secured to a piston rod 5.2 1 which passes through a packing 425 which is maintained under pressure by packing gland 126. The coolant leaves and enters a chamber 409 through inlet and outlet 408.

The operation of this external combustion gas engine is as follows:

It being assumed that the valve I2 of the thermostatic fuel control device Ti and valve 65 of pressure ratio fuel control device 55 are open and fuel is flowing through pipe 15 and 16 to burner I8, the engine may be started by man'- ually lighting burner 18 and manually turning shaft 27. In lieu of manual starting, conventional electrical means (not shown) may be used, such as a starting motor for rotating fly wheel 32 and either a hot wire, or spark gap may be employed to ignite burner l8.

Operation of air blower 35 forces air to support combustion through heat exchange unit 3'! to burner l8, and thence to combustion chamber 40. The products of combustion flow throughpassages 34!, thus heating the hot cylinder head 3. The gas contained in portion is of cylinder E5 of the thermo-gas compressing unit I will be heated by the heat conducted through cylinder head 3. The reciprocation of the gas moving plunger 2 in cylinder 15 by its connected mechanical linkage will cause, upon a downward. stroke of the plunger, the heated gas to flow through radial passages 30%, the elongated passages 5. of the heat regenerator, and passages 406, located in the cold cylinder head I. As the gas is moved through the regenerator a certain amount of the heat is absorbed and additional amounts of heat are absorbed by the coolant in passage 409 of the cold cylinder head as the gas passes through radial passages Thus the gas which reaches chamber H of cylinder 15 is reduced in temperature and the resulting drop in pressure causes gas to be drawn through pipe 12, check valve i3, pipe 5! from receiver 50. Upward movement of the gas moving plunger 2 causes the cooled gas in chamber ii to flow through radial passages 466, the elongated passages of heat regenerator 5 and the radial passages 304 to chamber [9 of cylinder i5. During this flow of gas the heat regenerator liberates heat to the flowing gas and upon reaching portion It after flowing through radial passage 304 the gas is elevated in temperature, and the pressure is correspondingly increased. As a result, the increase in pressure causes a portion or the gas confined in cylinder !5 to flow from the cylinder through pipe 12, check valve l4, pipe BI, into receiver 60. Repeated strokes of the gas moving plunger 2 thus cause an appreciable amount of gas to be pumped from receiver 50 into receiver 50 and thus a definite pressure ratio is built up between the gases in the two receivers. As the pressure builds up in receiver 60, gas flows through check valve H0 or" connection i 26, pressure control mechanism i23, pipe III, to auxiliary compressed gas motor fit. The gas under pressure acts through piston valve 3|, upon piston 2!, to cause it to reciprocate within its cylinder. Motor 20 is mechanically linked, as heretofore described, with flywheel 32, gas moving plunger 2 and auxiliary gas compressor 90. The movement of piston rod 22 thus causes plunger 2 to reciprocate in cylinder 15, and also causes piston 9| to operate in cylinder 9'4 of the compressor 00. Operation of the compressor 90 serves to pump gas from receiver 50 into receiver 80. The path of the gas during this pumping operation is from receiver 50, through pipe H3, heat interchanger i353, valve chest I05, pipe H2, the valve chest 39 of compressed gas motor 20, pipe Ml, valve M0, pipe 86, inlet valve 92, cylinder 90, discharge valve 93, pipe 8|, connection I21, to receiver 80. Continued operation of the auxiliary gas compressor 90 serves to increase the pressure in receiver and to reduce the pressure in receiver 50 which in turn causes a reduction of pressure in the thermo-gas compressing unit I and the receiver 60. When the pressure in receiver 50 falls below atmospheric pressure, check valve 84 of unloader valve 35 opens to permit atmospheric air or other gas as previously described to be drawn into pipe 86 and to be pumped into receiver 8o through pipe BI. The continued operation of auxiliary gas compressor til builds up the pressure in receiver 80 until diaphragm 32 is extended against a lever which is set for a predetermined pressure in receiver til. When this pressure is attained, diaphragm 32 will be extended and check valve actuator 83 will move to close check valve 8 3.

As auxiliary gas compressor 38 continues to operate pipe 86 and the connecting lines will be evacuated down to the point where compressor 90 becomes inoperative. The reduction of pressure in receiver 58 affects diaphragm 52 and permits the opposing diaphragm 62 to move the valve rod 56 to close valve 65. Closure of valve 65 reduces the flow of fuel to burner I8 to an amount which is just sun cient for idling operation. The thermo-gas compressing unit and the auxiliary motor and pump will continue to operate in this manner under idling conditions as long as the throttle valve I22 remains closed.

Gas engine IIIIl is started by opening valve I20 which permits compressed gas from receiver GII to flow through check valve H9, connection I28, pipe I32, valve I2Il, and pipe IZI, to the valve chest I05. The exhaust from the engine flows through pipe H3 and the heat interchanger I35 to receiver 50. Flow of compressed gas to valve chest I95 serves to initiate operation of the engine which results in rotation of crank shaft IIiIi. When valve I29 is partially opened and a light torque is applied to crank shaft ltd material pressure difference exists in pipe i332 and IEI across the valve I20, piston 28 which is affected by the pressure in receiver 6t remains in the position shown in Fig. l, i. e., spring I252 is compressed and piston rod I29 is positioned to maintain valve I40 in an open position and valve I30 in a closed position. When increased torque is applied to the crank shaft wt and the throttle valve I28 is in a partially open. position, the pressure in pipe I2! builds up in respect to the pressure in pipe I32. Under this operating condition compression spring I24, plus the increased pressure existing in pipe I22, serves to move piston I28 of the pressure control mechanism I23 to close valve I40 and open valve I30. This permits gas from receiver 86 to flow through connections I2! and I26, pipe I32, throttle valve I2t, and pipe IZI, to gas engine I959. The increased pressure from receiver ti! serves to operate engine IIIG at the increased output torque. As the engine comes up to speed under the increased load the pressure differential across valve I20 is partially restored and piston lie is moved to compress spring IN. This action serves to close valve I39 which will remain closed until greater torque is required.

If materially less torque is required, the pressure differential across valve I26 is increased and piston I28 will move to the extremity of the cylinder to further compress spring I2 4, The resultant movement of piston rod I29 serves to move the toggle connection It! to open valve Mill. The opening of valve use completes a flow path from receiver E! to receiver 89 via the auxiliary gas compressor cc, as previously explained. Operation of the compressor serves to decrease the pressure of the gas in receiver 50 which again reduces the pressure differential across throttle valve I29 and also on opposite sides of piston I28, thus allowing spring I24 to move piston I28 to close valve I40. During this latter operation, valve I30 has remained closed, due to the lost motion in toggle connection I3I, which is operated by the piston rod I29. This condition of operation continues until a change of torque occurs on the output shaft of gas engine I00, or until the setting of the throttle valve IZt is changed.

Increased opening of the throttle valve I 20 will decrease the pressure differential across the valve, and piston I28 will operate in the manner described as a function of the pressure differential to open valve I 30. This results in raising the pressure of the gas supplied to gas engine I00 which causes the motor to accelerate. As the motor accelerates the flow of gas in pipe IZI increases, which serves to re-establish the pressure differential across throttle valve It'd. Thus it will be apparent that the speed of engine Iiiil is maintained substantially proportional to the throttle valve opening.

The opening of throttle valve I2I3 as above described also results in a lowering of the pressure differential existing between receivers 60 and 50. Since the pressure existing within these two receivers actuates the diiferential pressure ratio fuel control valve 65, it will be apparent that an increase of pressure in receiver 59 and its resultant eiTect on diaphragm 52 will serve to overcome the opposed force on diaphragm 62 resulting in the opening of valve 65 to permit an increased fuel flow to burner I8. Valve 65 remains open as long as the ratio of pressure in receivers 5i! and (it remains below a predetermined value. As increased fuel is fed to burner l8, the temperature developed in combustion chamber 50 is raised; this increases the temperature difference between the hot and cold ends of cylinder I5 which in turn increases the volumetric efficiency of the compressing unit to meet the demands of gas engine Hi0.

When the hot cylinder head 3 attains its working temperature, the thermostatic fuel control device 71 influenced by the expansion of fluid in bulb H3 comes into operation to maintain the desired temperature of hot cylinder head 3 by controlling the operation of valve 12 in the fuel supply line. Thus the thermostatic fuel control device 1'! serves as a control to maintain the temperature of hot cylinder head 3 substantially constant during varying load conditions upon the external combustion gas engine. Increased loading of the engine will result in increased heat transfer by the gas in cylinder I5 and decreased loading of the engine will result in a lowering of heat transfer by the gas in cylinder I5. Since an increase in the opening of throttle valve I20 serves to speed up engine I and its accessories, the output of blower 35 will be increased to supply the necessary combustion air to burner I8.

When the throttle valve I28 is closed after gas engine I98 has been in operation, the components of the external combustion gas engine are automatically placed in idling or stand-by condition. Since the closure of valve I28 decreases the flow of gas from receiver BI] and the operation of the thermo-gas compressing unit continues to pump gas from receiver 58 into receiver 69, the pressure ratio existing between these receivers is increased and the pressure ratio fuel control valve 65 is actuated as a result of this pressure ratio to decrease the supply of fuel to burner I8. Upon decrease of fuel the temperature of hot cylinder head 3 decreases which in turn results in a decrease in the ratio between the temperatures of the cold and hot cylinder heads. As the term perature differential is decreased between the hot and cold cylinder heads of the thermo-gas compressing unit I, the pressure ratio will also be reduced to the predetermined value which is required to be maintained in the receivers 50 and 60 for idling conditions.

Confined spaces may be readily heated by the air used to absorb heat from the coolant which flows through heat exchange unit 3 Hi. This absorbed heat is removed from the cold end of the thermo-gascompressing unit and comprises that heat which must be discarded in any heat engine. The coolant flowing in the jacket or chamber of the cold cylinder head and through the heat exchange unit 3; may comprise water or any suitable low freezing point liquid, which is normally employed in the cooling system of an internal combustion engine. Additionally, the coolant may be a gas, such as air, which will serve as a heat transfer medium. In View of the fact that the exhaust gas flowing from gas engine 100 through pipe H3 to receiver 50 has a low temperature, the heat exchange unit l35 positioned in pipe H3 may be employed for cooling pur poses. This refrigerating effect may be utilized to cool any fluid entering the heat exchange unit I35 at I33 and leaving through the outlet pipe !34. Thus, a confined space located a distance from the heat exchange unit E35 may be cooled by the passage of the cooled fluid through a heat exchanger in the form of a conventional radiator, or air may be forced through inlet 33 and outlet pipe I34 to obtain directly the refrigerating effect.

Pistons H12 and valves llil of gas engine Hill are preferably lubricated by oil or other flowable lubricant positioned within the closed gas circuit between receivers. 50 and 60. Operation of the thermo-gas compressing unit i may serve to draw oil through pipe 5| from receiver 50 which will pass through check valves l3 and i l and be returned to receiver 69 through pipe 5|. During operating of gas engine I00 this lubricant will pass through check valve Hi connection I26, pipe 532, valve no and pipe l2! to engine ms. Further, a portion of the lubricant will flow from receiver 60 through pipe Hi to the auxiliary compressed gas motor 25%, pipes H ll and 86, to the auxiliary gas compressor 98 and then to receiver 8! In this manner the gas engine [00 and the auxiliar devices will be automatically lubricated during their operation. The lubricant will be circulated without being unduly heated or contaminated by contact with ambient air.

The employment of an inert gas in the closed gas flow system of the engine as has previously been discussed eliminates the possibility of corrosion of the working parts and in addition prevents the deterioration of lubricants due to oxidation.

The aforedescribed external combustion gas engine will operate at an eificiency which closely approaches the theoretical value of the efficiency of reversible heat engines which is expressed by the following equation:

wherein T1 is the temperature of the gas in chamber In of cylinder l5 and T2 is the temperature of the gas in chamber I! of cylinder l5. The

radiant heat transferred through gas moving plunger 2 is reduced to a negligible quantity due to the construction of the plunger as previously described. Passage of the flue gases from combustion chamber 40 and air from blower 35 through the heat exchanger 31 serves to remove substantially all of the available heat from these flue gases, and to heat the combustion air so that low quality fuels may be efiiciently used. Losses due to either conduction or radiation from the combustion chamber, cylinder l5, and the hot end of heat exchanger 31 are minimized due to the use of adequate heat insulating material about these parts in accordance with insulating practices well known in the art. The temperature of the hot cylinder head is raised to a high value due to the use of heat conductive material which is corrosion resistant at high temperatures. In view of these measures taken to conserve heat energy and to maintain as great a temperature difference as is possible between the opposite ends of cylinder i5, this external combustion gas engine will operate at an efficiency which closely approaches the theoretical limit as expressed in the above equation.

I claim:

1. In a heat exchange device having a plurality of substantially parallel flow paths alternate paths of which are diagonally directed with respect to the adjacent paths, the combination comprising, a plurality of pairs of heat conducting sheets positioned in superimposed relationship, each of said heat conducting sheets being identically shaped and formed with a substantially rectangular contour and provided with an aperture adjacent to each corner thereof, raised portions formed at diagonally opposite corners of said sheets surrounding said apertures, depressed portions formed at the remaining diagonally opposite corners of said sheets surrounding said apertures, said pairs of heat conducting sheets positioned with the diagonally positioned raised portions in fluid tight contact and with the apertures therein located in alignment, a spacing ring having radial openings therein positioned between the pairs of sheets within the recesses formed by the diagonally positioned depressed portions and around the edge of said apertures, means forming a fluid tight connection between the outside edges of said sheets, and means to secure said sheets and spacing rings in the aforedefined position.

2. In a heat exchange device having a plurality of substantially parallel flow paths alternate paths of which are diagonally directed with respect to the adjacent paths, the combination comprising, a plurality of pairs of heat conducting sheets positioned in superimposed relationship, each of said heat conducting sheets being identically shaped and formed with a substantially rectangular contour and provided with an aperture adjacent to each corner thereof, raised portions formed at diagonally opposite corners of said sheets surrounding said apertures, depressed portions formed at the remaining diagonally opposite corners of said sheets surrounding said apertures, said pairs of heat conducting sheets positioned with the diagonally positioned raised portions in fluid tight contact and with the apertures therein located in alignment, a spacing ring having radial openings therein positioned between the pairs of sheets within the reces es formed by the diagonally positioned depressed portions and around the edge of said apertures, means'forming a fluid tight connection between the outside edges of said sheets, face plates positioned on sides of said superimposed heat conducting sheets having openings therethrough in alignment with said apertures in said heat conducting sheets, and means extending through said plates and sheets for securing the heat exchange elements in position.

3. A heat exchange device comprising a plurality of pairs of identically shaped, substantially rectangular sheets positioned in superimposed relationship between face plates, each of the sheets comprising said pairs being formed of substantially fiat heat conducting material and provided with depressed sections located adjacent to diagonally opposite corners and with raised sections located adjacent to the other opposite corners of the rectangular sheet, each of said raised and depressed sections provided with a centrally positioned opening through said material, said sheets of each pair positioned with the depressed sections thereof in engagement with each other and the openings therein in alignment and with the raised sections thereof in engagement with and the openings therein in alignment with the apertured raised sections of the adjacent pair, spacing rings having openings in the side walls thereof positioned within said raised portions and extending between the sheets of each pair and between the aligned depressed sections of the sheets of adjacently positioned. pairs, closure means for sealing the peripheral edges between said superimposed flat sheets and openings positioned within said face plates in alignment with the openings in said sheets whereby a plurality of passages are provided between the openings positioned adjacent to diagonally opposite corners of said sheets which are in heat exchange relation with a second group of passages extending between said other diagonal corners of said plates.

4. A heat exchange device comprising a plurality of pairs of identically shaped, substantially rectangular sheets positioned in superimposed relationship between face plates, each of the sheets comprising said pairs being formed of substantially fiat heat conducting material and provided with depressed sections located adjacent to diagonally opposite corners and with raised sections located adjacent to the other opposite corners of the rectangular sheet, each of said raised and depressed sections provided with a centrally posi tioned opening through said material, said sheets of each pair positioned with the depressed sections thereof in engagement with each other and the openings therein in alignment and with the raised sections thereof in engagement with and the openings therein in alignment with the apertured raised sections of the adjacent pair, spacing rings having openings in the side walls thereof positioned within said raised portions and extending between the sheets of each pair and between the aligned depressed sections of the sheets of adjacently positioned pairs, closure means for sealing the peripheral edges between said superimposed flat sheets, a plurality of tightening means extending between said face plates and through said superimposed flat sheets provided with a spacing washer positioned between each of said sheets for securing said pairs and plates, and openings positioned within said face plates in alignment with the openings in said sheets Whereby a :plurality of passages are provided between the openings positioned adjacent to diagonally opposite corners of said sheets which are in heat exchange relation with a second group of pas- 18 sages extending between said other diagonal corners of said plates.

5. A heat exchange device having two series of passages for the flow of separate fluids in an opposed diagonal direction through said passages comprising a plurality of identically shaped sheets, each of said identically shaped sheets having a, generally rectangular contour, being formed of heat conducting material having raised sections located a spaced distance from the edges of diagonally opposite corners, having depressed sections located a spaced distance from the edges in the other opposite corners of the sheet and apertures extending through said sheets within said raised and depressed sections, adjacently positioned identically shaped sheets arranged in spaced superimposed relation with corresponding depressed sections in engagement with each other and the apertures therethrough in alignment to provide passages located in diagonal corners of said sheet communicating between said adjacently positioned sheets and with opposite diagonally positioned raised sections and apertures therein in alignment with each other, a spacing ring provided with openings in the side wall thereof positioned between said aligned raised section and around the aligned apertures of each of said adjacently positioned sheets, and closure means located adjacent the edges of said sheets to seal the spaces therebetween.

6. A heat exchange device comprising a plurality of generally rectangular sheets formed of heat conducting material positioned in spaced superimposed relation to define a plurality of passageways between adjacently positioned sheets, means positioned adjacent the edges of said sheets to seal the spaces between each of said sheets, each of said heat conducting sheets having raised sections located a spaced distance from the edges 1n diagonally opposite corners and depressed sections located a spaced distance from the edges in the other opposite corners of the sheet, said raised and depressed sections provided with apertures extending through said sheets, said adjacently positioned sheets arranged with the corresponding depressed sections in engagement with each other and the apertures therethrough in alignment to provide openings located in diagonal corners of said sheets which communicate between alternate passageways and with the opposite diagonally positioned raised sections and apertures therein in alignment with each other, and a spacing ring provided with openings in the side wall thereof positioned between said aligned raised sections and around said apertures of each of said adjacently positioned sheets.

ORSON A. C'ARNAHAN. References Cited in the file of this patent UNITED STATES PATENTS Number 

